Various types of surgical procedures are currently performed to investigate, diagnose, and treat diseases of the heart and the great vessels of the thorax. Such procedures include repair and replacement of mitral, aortic, and other heart valves, repair of atrial and ventricular septal defects, pulmonary thrombectomy, treatment of aneurysms, electrophysiological mapping and ablation of the myocardium, and other procedures in which interventional devices are introduced into the interior of the heart or a great vessel.
Many of these procedures require a gross thoracotomy, usually in the form of a median sternotomy, to gain access into the patient's thoracic cavity. A saw or other cutting instrument is used to cut the sternum longitudinally, allowing two opposing halves of the anterior or ventral portion of the rib cage to be spread apart. A large opening into the thoracic cavity is thus created, through which the surgical team may directly visualize and operate upon the heart and other thoracic contents.
Surgical intervention within the heart by a thoracotomy generally requires isolation of the heart and coronary blood vessels from the remainder of the arterial system, and arrest of cardiac function (an “open heart” procedure). Usually, the heart is isolated from the arterial system by introducing an external aortic cross-clamp through a sternotomy and applying it to the aorta between the brachiocephalic artery and the coronary ostia. Cardioplegic fluid is then injected into the coronary arteries, either directly into the coronary ostia or through a puncture in the aortic root, so as to arrest cardiac function. In some cases, cardioplegic fluid is injected into the coronary sinus for retrograde perfusion of the myocardium. The patient is placed on cardiopulmonary bypass to maintain peripheral circulation of oxygenated blood.
Of particular interest are intracardiac procedures for surgical treatment of heart valves, especially the mitral and aortic valves. Tens of thousands of patients are diagnosed with aortic and mitral valve disease each year. Various surgical techniques may be used to repair a diseased or damaged valve, including annuloplasty (contracting the valve annulus), quadrangular resection (narrowing the valve leaflets), commissurotomy (cutting the valve commissures to separate the valve leaflets), shortening mitral or tricuspid valve chordae tendonae, reattachment of severed mitral or tricuspid valve chordae tendonae or papillary muscle tissue, and decalcification of valve and annulus tissue. Alternatively, the valve may be replaced by excising the valve leaflets of the natural valve and securing a replacement valve in the valve position, usually by suturing the replacement valve to the natural valve annulus. Various types of replacement valves are in current use, including mechanical and biological prostheses, homografts, and allografts. Valve replacement, however, can present a number of difficulties including that the invasiveness of the procedure can lead to long recovery times and that the irregular shape of the valve annulus can cause difficulty in properly fixing and orienting the replacement valve, which can lead to leaks and other problems. Therefore, in situations where patients can adequately be treating by repairing, rather than replacing, the valve, it is generally preferable to do so.
The mitral and tricuspid valves inside the human heart include an orifice (annulus), two (for the mitral) or three (for the tricuspid) leaflets and a subvalvular apparatus. The subvalvular apparatus includes multiple chordae tendineae, which connect the mobile valve leaflets to muscular structures (papillary muscles) inside the ventricles. Rupture or elongation of the chordae tendineae results in partial or generalized leaflet prolapse, which causes mitral (or tricuspid) valve regurgitation. A commonly used technique to surgically correct mitral valve regurgitation is the implantation of artificial chordae (usually 4-0 or 5-0 Gore-Tex sutures) between the prolapsing segment of the valve and the papillary muscle. This typically open heart operation is generally carried out through a median sternotomy and requires cardiopulmonary bypass with aortic cross-clamp and cardioplegic arrest of the heart, as described above.
Using such open heart techniques, the large opening provided by a median sternotomy or right thoracotomy enables the surgeon to see the mitral valve directly through the left atriotomy, and to position his or her hands within the thoracic cavity in close proximity to the exterior of the heart for manipulation of surgical instruments, removal of excised tissue, and/or introduction of a replacement valve through the atriotomy for attachment within the heart. However, these invasive open heart procedures produce a high degree of trauma, a significant risk of complications, an extended hospital stay, and a painful recovery period for the patient. Moreover, while heart valve surgery produces beneficial results for many patients, numerous others who might benefit from such surgery are unable or unwilling to undergo the trauma and risks of current techniques.
Techniques have been developed and are under development for minimally invasive thorascopic repair of heart valves while the heart is still beating. Int'l Pub. No. WO 2006/078694 A2 to Speziali discloses a thorascopic heart valve repair method and apparatus. Instead of requiring open heart surgery on a stopped heart, the thorascopic heart valve repair methods and apparatus taught by Speziali utilize fiber optic technology in conjunction with transesophageal echocardiography (TEE) as a visualization technique during a minimally invasive surgical procedure that can be utilized on a beating heart. U.S. Publication No. 2008/0228223 to Alkhatib also discloses an apparatus for attaching a prosthetic tether between a leaflet of a patient's heart valve and another portion of the patient's heart to help prevent prolapse of the leaflet and/or to otherwise improve leaflet function.
More recent versions of these techniques are disclosed in U.S. Patent Application Publication Nos. 2009/0105751 and 2009/0105729 to Zentgraf, which disclose an integrated device that can enter the heart chamber, navigate to the leaflet, capture the leaflet, confirm proper capture, and deliver a suture as part of a mitral valve regurgitation (MR) repair. These references are hereby incorporated by reference herein in their entirety.
An alternative to the above-described techniques that insert a suture through a single valve leaflet and anchor the suture to the heart is an edge to edge valve repair. In a traditional Alfieri edge to edge procedure, the edges of adjacent valve leaflets are sutured together to coapt the leaflets using an open surgical approach. This technique has been mimicked in minimally invasive, beating heart procedures by employing a clip that joins the leaflets together rather than a suture. U.S. Patent Publication No. 2004/0044365 to Bachman discloses a technique for minimally invasively accessing the heart through an endovascular approach to perform and edge to edge repair. After sutures are inserted into the leaflets, the sutures can be knotted external to the patient's body and advanced to the repair site with a knot-pushing device as shown, for example, in U.S. Pat. Nos. 8,202,282 and 8,075,574. However, it has been found that it can be difficult to stabilize the leaflets to maintain appropriate tension when knotting sutures in such a fashion and that it can be difficult for the knot pusher to properly advance the knot all the way to the leaflets. In addition, use of such a knot pusher risks damage to other structures within the heart. There is therefore a need for a technique for performing an edge to edge repair on a beating heart of a patient that secures the leaflets together at a proper tension in a more effective manner.